1. Field of the Invention
This invention concerns baffle assemblies useful inside cavities or other open areas of metal structures wherein the baffle assembly may be readily temporarily held in place by magnetic attachment. More particularly, the present invention concerns a baffle assembly having a layer of flexible thermally expandible material and an adjacent layer of flexible magnetic material which permits the baffle to be made into a desired shape and temporarily held against a ferromagnetic metal prior to expansion.
2. Description of the Prior Art
The use of baffle assemblies in automobiles is well known to inhibit sound transmission through panels, pillars, rails and the like of a chassis or unibody structure. While rigid foam materials were initially employed in the cavities, it is now known to use thermally expansible baffle compositions which undergo heat induced expansion to expand in the cavity. Such heat activation may occur when the automobile is passed through a paint baking oven forming a part of the primer or paint curing step of the automobile manufacturing process. Various types of materials have been used, including the dry expansible sealant and baffle composition and product disclosed in U.S. Pat. Nos. 5,266,133 and 5,373,027.
However, the thermally expansible baffle composition must typically be placed in a particular location within the cavity of the vehicle to be effective. After activation and expansion of the baffle composition, it readily conforms to the surrounding panels and adheres thereto, but prior to activation the composition must be at least temporarily held in place. This has required the use of a separate carrier or component on which the thermally expansible baffle composition is mounted, and which in turn is mounted on the vehicle. Examples disclosing various types of parts and components for retaining a baffle composition in place include those shown in U.S. Pat. Nos. 5,506,025 and 5,806,915. These carriers attach to the expansible baffle composition, but require a hole in the surrounding structure for mounting. Such holes may therefore permit the intrusion of corrosion forming agents therethrough. In addition, primer and other coatings applied to the metal inhibit adhesive attachment.
There have also been developed mounts for insertion into a hollow space of a hollow structure such as a vehicle pillar, which mounts include an expandable foam substrate and at least one support panel secured to the substrate using a tack as shown in U.S. Pat. No. 5,904,024. The mount is then secured to the interior wall of the hollow space through either a clip, a magnet, or a suction disc. However, this construction uses a magnet to hold the support panel to the interior wall and not the expansible material itself. There have also been developed magnetized hot melt adhesive articles such as shown in U.S. Pat. Nos. 5,985,435, 4,427,481, 4,724,243 and 4,749,434 which are used to seal a gap or opening in an automobile part, which include thermoplastic resins, tackifiers and the like with magnetized particles to form an extruded mixture. However, these adhesive articles do not satisfy the needs hereof for an initially non-tacky expansible baffle composition.
Thus, there has developed a real need for a baffle composition which may be temporarily secured in place prior to activation, may conform to the surrounding structure prior to activation, is inexpensive to produce, and does not require holes through the structure.
These needs have largely been met by the expansible synthetic resin baffle with magnetic attachment of the present composition. That is to say, the baffle hereof is simple, inexpensive to manufacture, convenient to install, requires no additional mounting structure or holes in the wall of the structure forming the cavity, and may be cut or formed to a desired shape.
Broadly speaking, the baffle of the present invention is provided as adjacent layers of magnetic material and expansible baffle material. The layers may be co-extruded to form the baffle, or molded into layers. The expansible baffle material is preferably an initially non-tacky thermally expansible material which activates at a temperature preferably within the range of about 100xc2x0 C. to about 200xc2x0 C., and which is resilient and flexible prior to expansion. Such a baffle material is disclosed in U.S. Pat. Nos. 5,266,133 and 5,373,027, the disclosure of which is incorporated herein by reference. The expansible material preferably expands to at least 300% and preferably 400% or more of its initial volume during baking. The baffle material may be provided as a relatively thin layer which may be conformed to irregular surfaces, or formed into a three dimensional part of a greater thickness which is pre-conformed to an irregular shape.
The magnetic material is in laminated relationship to the baffle material, whereby the baffle material and magnetic material is side-by-side. The magnetic material may be provided as strips which may cover all or only a portion of the baffle material. Further, the magnetic material is preferably flexible to conform to irregular shapes. The magnetic material may also be perforated to permit enhanced bonding between the baffle material and the wall of the structure after activation and cooling, thereby providing an enhanced bonding between the expanding baffle material and the structure. Advantageously, the magnetic material retains its position in proximity to the wall of the structure throughout the expansion period, and thus the magnetic attachment of the magnetic layer is unaffected by the expansion.
The baffle of the present invention is simple to install, and involves merely placement in a desired position and permitting the magnetic material to attach to the wall of the structure. The structure needs only some ferromagnetic material in sufficient proximity to the baffle to permit magnetic attraction, and thus its use includes not only application to steel and other ferromagnetic metals, but also to compositions with a ferromagnetic metal backing or core. Because no adhesive or holes are required, there is no problem with reapplying or repositioning the baffle. The baffle""s application is not limited to automotive uses, but may include placement in marine environments as well as in appliances or the like where sound deadening is desired. These and other advantages will be readily appreciated by those skilled in the art with reference to the drawings and description which follow.